Starting and controlling device for electric motors



(No Model.)

J. W. MOORE.

STARTING AND CONTROLLING DEVICE FOR ELECTRIC MOTORS.

Patented July 24, 1894.

FigZ- WITNESSES- N MW W JAAM UNITED STATES PATENT OFFICE.

JOSEPH W. MOORE, OF BOSTON, MASSACHUSETTS.

STARTING AND CONTROLLlNG DEVICE FOR ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent No. 523,586, dated July 24,1894.

Application filed April 25, 1894. Serial No. 508,993 (No model.)

To aZZ whom it may concern.-

Be it known that I, JOSEPH W. MOORE, a citizen of theUnited States,residing atBoston, in the county of Suffolk and State of Massa-'chusetts, have inventedcertain Improvements in Starting and ControllingDevices for Electric Motors, of which the following is a specification.

My invention relates to certain improvements in controlling devices forelectric motors, and is adapted particularly for use on electric motorsfor constant potential circuits employed for operating elevators Wherethe motor is started and stopped at the will of the operator from thecar or platform.

It is well known that in shunt-wound motors the armature is of very lowresistance, making it necessary to interpose in the armature-circuit avariable resistance which can be gradually cut out as the motor gets upto speed. In starting, there is enough resistance in the rheostat tokeep the current down Within the capacity of the armature I wires, andas the armature starts and accelerates in speed, thecounter-electro-motive force increases and permits of the cutting out ofthe said armature resistance. Should there be no outside resistance inthe armature-circuit, or should the resistance be cut out faster thanthe acceleration of the speed of the armature and consequently fasterthan the counter-electro-motive force (which is dependent on the speedof the armature) could generate and keep down the current within thesafety limit, the safety catches would fuse, causing the inconvenienceand expense of replacing them, or possibly causing injury to thearmature or to the insulation on the line. Of course this difficulty iseasily overcome in the case of stationary motors where the attendant canstand at the rheostat within sight of the motor and by watching themotor, cut out the resistance by hand at the same rate at which thearmature gets up to speed; but where the conditions are such that themotor is not in sight of the operator, which is the case in thecontrolling of electric motors on elevator machinery, it is apparentthat some automatic device is necessary for retarding the operation ofcutting out said pesistance in such a manner that the operator cannot bycutting out the resistance too rapidly cause an abnormal amount ofcurrent to be admitted to the armature circuit, thus causing a jumpingof lights which may be on the same circuit with the motor, or otherwiseinjuring the service on the circuit. In order to overcome thesedifficulties and to accomplish the desired results stated above, manydevices have been invented which are more or less defective.

I will here mention so me of the devices which have for their object toproperly start and control shunt-wound constant potential motors, andcall attention to some of the points wherein they fail to accomplish theresult sought.

A resistance connected to blocks, said resistance being cut outsuccessively on said blocks by the contact of brushes attached to an armand leading the current off to the armature of the motor, is common toall. Now

it becomes necessary to automatically move the said arm across the saidcontact-blocks and to retard its movement so that the motor will havesufficient time to accelerate in speed as fast as the resistance isbeing cut out. One, among the Various ways of accomplishing this, is tohave the operator by means of a rope or lever connected with themachine, release a weight, which by gravity gives motion to a rheostatarm, the movement of said weight being retarded by an oil dash-pot orair suction or compression, or by equivalent means. In other devices asolenoid is employed, whereby the operator in the usual manner appliesby means of a rope or lever, the current to said solenoid, which in turnactuates the rheostat arm, the action of the solenoid being retarded bya dash-pot, a balance wheel or a centrifugal or other mechanical device.

In the cases mentioned it is obvious that when the rheostat arm isreleased or the automatic device given control of the rhcostat, providedthe device operates as intended, the rheo'stat arm will continue itsmotion until the resistance is all cut out, and should the motor be tooheavily loaded or for any other cause refuse to start, the current wouldexceed the safety limit and blow out the fuses or burn out the armature,which is obviously a serious defect.

In the devices where oil retarders are employed, other defects areapparent inasmuch as the oil wastes away, causing the resistance to becut out too rapidly, or is influenced by the weather, congealing whencool and cansing the apparatus to stick and stop.

In view of the above named facts it is evident that an automaticstarting and controlling device for electric motors, to be perfect, mustcutout the resistance only at such a rate that the safety limit ofcurrent cannot be exceeded, or in other words the rheostat arm must keeppace with the increasing speed and consequent increasingcounter-electromotive force of the motor, and should the m0- tor refuseto start or cease to accelerate, the rheostat arm should remain at thepoint reached when acceleration ceases.

Having explained the objects to be attained and some of the most seriousdefects of existing apparatus, ll will proceed to describe my inventionwhich obviates the difticulties referred to and attains the desiredresults above stated.

Figure 1 is a side elevation of my improved starting and controllingdevice, showing the motor and wiring in diagram. Fig. 2 is a sideelevation representing a modification of my invention.

A represents the motor shown in diagram.

8 is the main armature circuit and 1 is the field circuit.

B is a switch by which the circuits of said motor are opened and closedat the will of the operator.

0 is the customary rheostat interposed in the armature circuit andconsisting of the contact-blocks Ct, a, connected to the resistance rand mounted on slate or other material insulating them from each other.i

D is the rheostatarrn pivoted at Z) and held in the position shown inFig. 1,by the stop 1 to include the total resistance in the circuit.

E, Fig. 1, is a differentially wound solenoid, its core F beingconnected with the arm D by means of the link G. The armD is alsoconnected to the frame I by the tension spring 11 and threaded rod Jprovided with nuts 6, 7.

The differentially wound solenoid E consists of two helixes K and L. Thehelix K is connected atthe switch B by the line 7 in a circuitpreferably leading directly from the positive to the negative side ofthe main line. The helix L is connected by the line so at the switch Bin a branch of the main armaturecircuit connecting therewith at f, Fig.1, said branch including said helix in parallel with the resistance r,and in series with the armature of the motor, thus making the currentinsaid helix dependent on the speed of the armature and consequentcounter-electrometive force generated by the motor, and independent ofthe strength or the current in the armature-circuit.

It is to be particularly noticed that in the operation of my device thestrength and op eration of the retarding helix are not dependent on thestrength of the current in the armature-circuit, inasmuch as that branchof the armature-circuit in which the helix L is interposed is ofconstant resistance and independent of the variable resistance '7';therefore the current in saidhelix and consequently the force of thesame is also constant until the armature starts,independent ol thestrength of the current which flows to said armature; and afterstarting, the current will gradually diminish in the helix L until themotor attains its maximum speed, said motor not attaining full speeduntil the resistance r is en tirely cut out.

To show if possible more clearly that the strength of the helix L is notdependent on the strength of the armature current, let it be supposedthat the resistance r is cut out exactly at the same rate as theacceleration of speed of the armature, then the current in the armaturecircuit would remain constant from the time the armature started; andnotwithstanding this fact the current in the helix L would graduallyweaken at the same rate of acceleration of the armature until theresistance r was entirely out out and the helix L practically shortcircuited, showing conclusively that the weakening of the said helix wasentirely due to the influence of the increasing counter-electro-motiveforce generated by the armature.

Supposing that the switch B is thrown to the position shown by thedotted lines, the current would then pass through the different circuitsof the apparatus in the following manner: starting at the switch 13, thecurrent passes by the line 2' through the field'wire of the motor andenergizes the fields. Bylineil it passes through the arm D, the whole ofthe resistance 0', through the armature and through switch 18 to thenegative side of the main line. By the line 1 it passes through thehelix K and thence directly to the negative side of the main line; andby the line w it passes through the helix L and thence to the line 3,uniting with the armature-circuit at f.

The helixes K and L are so wound or corn nected that the current is madeto pass through them in opposite directions, and they are soproportioned that the action of one upon the core F is neutralized bythat ol' the other upon said core so long as the armature of the motorremains stationary.

The resistance r is such that when the switch is thrown as above stated,suilicient current will pass through the armature circuit to start themotor, and as soon as the motor armature commences to rotate then thestrength of the current in the helix L will be diminished bv theinfluence of the counter-electromotive LOI'GG thus generated, and thestrength of the current in said helix will continue to decrease at thesame rate that the speed of the motor accelerates, thus allowing thehelix K, the current in which remains constant, to act upon the core Fof the solenoid E with correspondingly increased strength, moving thearm I) across the contacts a, a, and over coming the resistance of thespring II and the weight of the core F until the resistance r is all cutout and the motor has attained its maximum speed. To secure a uniformmovement of the arm D, I adjust the spring 11 to the desired tension bymeans of the threaded rod J and nuts 6 and 7.

Fig. 2 represents a modification of my invention which is identical withthe construction shown in Fig. 1, excepting that the arm D forms a partof a T-shaped lever S pivoted at b, and that the helix K is made tocontrol a separate core P connected to the arm 10 of the lever S at d bythe link g, while the core F of the helix L is connected at h to the arm12 of the lever S by a link 'i. It is obvious that the result is thesame as if both helixes were arranged one within the other, and adaptedto control a single core as shown in Fig.1, the helix L acting as beforedescribed in opposition to the helix K, and exerting a retardinginfluence on the actuating force of the rheostat arm D.

The principal feature of my invention is the employment of two helixes,one of which, K, furnishes the actuating force of the rheostat arm andthe other of said helixes L being adapted to neutralize the effect ofthe helix K until the motor has attained sufficient speed to permit of afurther cutting out of the rheostat-resistance.

I do not wish to confine myself to the arrangement of the helix circuitsexactly as shown, as it is evident that the helix K could be included inany circuit,the current of which would act with sufficient force to movethe arm D and not diminish at so fast a rate as the current in the helixL.

I What I claim as my invention, and desire to secure by Letters Patent,is

1. In a starting and controlling device for electric-motors, thecombination of an armature-circuit divided into two branches or lines, arheostat consisting of a variable resistance included in one of saidbranches and a contact-arm adapted to cut in and out said variableresistance, a helix or solenoid included in the other branch of saidarmature-circuit, said helix being connected in parallel with saidvariable resistance and in series with the armature, and a second helixor solenoid connected with and adapted to actuate said con tact arm tocut in and out said variable resistance, but controlled by the firstnamed helix, substantially as set forth.

2. In a starting and controlling device for electric motors, thecombination of the armature-circuit divided into two branches or lines,a switching device for closing and opening the circuit through which thecurrent passes to the motor, a variable resistance in thearmature-circuit, a contact-arm adapted to cut in and out said variableresistance, a helix or solenoid included in a shunt of thearmaturecircuit and having its core connected with said contact-arm tocontrol the movement of the same, and a second helix or solenoidcontrolled by the first named helix, the latter being dependent on theinfluence of the counter-electro-motive force of the armature andentirely independent of the strength of the current in thearmature-circuit, substantially as set forth.

3. In a starting and controlling device for electric motors, thecombination of an armature-circuit divided into two branches or lines, avariable resistance or rheostat included in one of said branches, adifferentially wound solenoid consisting of two helixes, one of saidhelixes being included in the other branch of the armature-circuit andconnected in parallel with said variable resistance and in series withthe armature, and the other helix being included in another circuit andcontrolled by the first named helix, and a contact-arm connected to thecore of the said solenoid and adapted to cut in and out said variableresistance, the movement of said contact-arm being controlled by saidsolenoid, substantially as set forth.

4.. In a starting and controlling device for electric motors, thecombination of the armature-circuit divided into two branches or lines,the switch B for closing and opening the circuit through which thecurrent passes to the motor, a variable resistance in one of thebranches of the armature-circuit, the pivoted contact=arm D adapted tocut in and out said variable resistance, the spring H connected with thecontact-arm, a helix or solenoid L included in a shunt of thearmature-circuit and having its core F connected with the contactarm D,whereby said solenoid is adapted to control the movement of the same,and a second helix K included in another circuit and adapted to becontrolled by the helix L, substantially as described.

5. In a starting and controlling device for electric motors, thecombination of the armature-circuit divided into two branches or lines,the switch- B for closing and opening the circuit through which thecurrent passes to the motor, a variable resistance in one of thebranches of the armature-circuit, the pivoted contact-arm D adapted tocut in and out said variable resistance, the spring H connected with thecontact-arm, and a differentially wound solenoid E having its core Fconnected with the contact-arm D,and consisting of two helixes K, L, thehelix L being included in the other branch of the armature circuit andconnected in parallel with the said variable resistance and in serieswith the armature,

and the helix K being included in another circuit and being controlledby the helix L, whereby the contact-arm is operated to cut out theresistance in proportion as the speed (315 tlllie motor increases,substantially as set Witness my hand this 20th day of April, A. D. 1894.

JOSEPH W. MOORE.

In presence of- P. E. TESOHEMAOHER, J. S. F. HUDDLESTON.

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